Method for the purification of titanium tetrachloride



Patented Mar. 14, 1944 UNITED STATES PAT 2,344,319 v METHOD FOR THE PURIFICATION OF TITANIUM TETRACHLORIDE Walter F. Meister, Elizabeth, N. J., assignor to National Lead Company, corporation of New Jersey New York, N. Y., a

to Drawing. Application September 1 1, 1942,

- Serial No. 457,970

.- 5 Claims. (01. 23-87) This invention relates to the-purification of titanium tertachloride.

Titanium tetrachloride in its pure form is a water-white liquid. The commercial products, however, which are obtained by chlorination of various available titaniferous materials, such as rutile, or residues-obtained from the extraction of iron from titaniferous iron ores, or of titaniferous iron ores themselves, are invariably contaminated with impurities which are carried over with the titanium chloride vapors duringthe chlorination process. The crude condensate of titanium tetrachloride usually has a strong yellowish color. 1

The magnitude and type of contaminants which will be found in the condensed vapors from the chlorination operation will depend upon the purity of the titaniferous material used and the method of chlorination.

A study of the chlorides of the elements of the various groups of the periodic system reveals that there are a number of elements besides titanium which may be reacted with chlorine to form volatile chlorides which will be carried over with the titanium tetrachloride vapors during the chlorination operation. Some of these chlorides may be more or less easily separated from the titanium tetrachloride condensate; those that are in solid form at ordinary temperatures and insoluble in the tetrachloride by settling and filtration, or both, and those which are miscible with the tetrachloride by fractional distillation. However, a separation of solid chlorides from titanium tetrachloride seldom effects complete removal of the chlorides and dependingupon the solubility of the respective chlorides they will be found in varying amounts as impurities in the titanium tetrachloride. Such impurities are not readily eliminated by distillation treatments because they tend to carry over with the vapors of titanium tetrachloride. Furthermore, fractional distillation to remove miscible-chlorides is not completely satisfactory because depending upon the vapor pressure of the respective chlorides they will tend to'distil over with the titanium tetrachloride and bev found in the condensate. One such chloride which, because of the proximity of its boiling point to that of titanium tetrachloride, cannot be separated by fractional distillation is vanadium chloride. Among the chlorides of other elements which tend to distil over with the titanium tetrachloride may be mentioned those of silicon, phosphorus, antimony and sulfur. Many of the contaminating chloride which, for the foregoing reasons,

.titanium, activated carbon,

may be found in titanium tetrachloride, impart discoloration. This is particularly true of vanadium tetrachloride.

That the discoloring impurities cannot be eliminated from titanium tetrachloride by straight fractional distillation is well-known, and various treatments for the elimination of such impurities, including vanadium, have been proposed in the priorart. Thus, purification of titanium'tetrachloride has been carried out by treatment with certain metals alone, such as iron in powder form, or with sodium amalgam prior to distillation. It has, however, been found that such treatments are not'entirely satisfactory, repeated treatments .and distillations being necessary for a substantially complete removal of these impurities.

Other purifying treatments for titanium tetrachloride, such as with diactivated inorganic compounds such as alumina, silica, or titanium dioxide, and certain organic compounds capable of polymerization have re ently been disclosed in the art.

It has now been discovered, according to the present invention, that impure titanium tetrachloride may be decolorized and purified to form a pure water-white liquid in a single treatment and single distillation by contacting with a hydrated iron sulfate which willyield water of hydration at temperatures below the boiling point of titanium tetrachloride.

Accordingly, it is among the objects of the present invention to produce in a single distillation a clear water-white pure titanium tertachloride. Other objects will be apparent from the following description.

According tothe present invention, the crude, impure titanium tetrachloride is mixed with a small amount of hydrated ferrous sulfate which will yield water of hydration at temperatures below the boiling point of titanium tetrachloride and the mixture heated under a reflux condenser at normal pressure. After sufilcient time has elapsed, for the treatment to take efiect, the titanium tetrachloride is recovered by a single distillation. The distilled liquid is water-white and free of impurities.

The hydrated ferrous sulfates which are suit able for the practiceof the invention are those which contain above one molecule of water of hydration. Thus, hydrated ferrous sulfate commonly known as copperas which generally contains about live or more molecules of water of and trichloride of hydration is well adapted for use in the present'invention and, li -des the relamum tively pure heptahydrate, FSO4.'7HaO, may be an em. Ground gg Oolorof W, used with'kespecially good results. Anhydrous T1014 rn di il t ferrous'sulfatean'dmonohydrate cannot'be used 1 a as such in theprac'tice of itgventiieci ntgut if PM these compounds are treated "w'a pror duce a degree of hydrationwhich, at tempera- 1 gift -"fa 4 Water-whit... tures below'the boiling point of titanium tetraggg 3 g M chloride,- i." e} about 136 0., yield water of hydra- 4111:: a, 1.0 3 n '1 tion, rush hydrated forms may be used.

In order to facilitate the.operation, mechani- The invention has in the foregoing been decal agitation may be employed or dry inert gases I may e bubbled through m during the scribed in connection with certain details of opiron sulfate'treatrnent and subsequent distllla-l emu-0n and-23mm? e am -al h b tion. Suspended. and colloidal matter and co"- moved should preferably be substantially elimlm that-are not included nated by, for example, fractional distillation prior $3 M??? claims z should to the iron sulfate treatment. Because of the m mm as m y as m reactivity of titanium tetrachloride'vapors with T invent! has been dggcribed with refer mm. it is preferable to carry ouvthe Admin ence to the treatment of titanium tetrachloride,

- but it should be understood that the other titation in a dry atmosphere. I

n so desired h iron lf t t t t may be nium halides, titanium tetrabromide and titanicarrled out under more than atmospheric pres- 5' tetra'flubnde may pinged in sure. In that case, gaseous reaction products I claim" should preferably be eliminated prior to the appncation of pressma 1. Method for purifying titanium tetrachloride The time and temperature of the treatment which comprises admixing with crude titanium tetrachloride a small amount of a hydrated ferrequired depends upon the amount of im urities present in the liquid and the amount of treating so mus sulfate wmch Yields watel; of hydration agent used. Ordinarily when contacting the crude temperatmes below abou- 136 boiling the titanium tetrachloride with the iron sulfate at mixture under refluxing copditions and then normal pressure at a temperature at or about mung the so'treated mamum tetrachmflde' treatment time of from about one hour to about which comprises admixing with crude titanium ,six hours is sufiicient with an amount of treating tetrachloride an ammmt' hydra'ted term! ferrous sulfate he to dmte sulfate which yields water of hydration at tem- :gfigm agout 5 grams F950 g gg t g g peratures below about 136 C. between about five of R804 er liter of liquid. The treatment of 40 grams and about tensrams. culated as ferrous this invention is very eflicient and a recovery of sulfate peso" Per .hter tetrachmride M11111! more than 95 percent of the titanium tetrachlothe ,mixture under efluxmg and than ride is attained in the single treatment and disdimming the tetrachlofldii- We awaitress; shss ss mazsiszfi The iron sulfate residue containing the impurities which have been removed from the titanium r g i g z an g i fermus sulfate tetrachloride may be treated for the recovery of y e e ween u grams and abwt m1 grams, calculated as ferrous sulfate, FeSOr, per Possible remain-mg -t1tanium tetrachloride and liter of tetrachloride, boiling the mixture under residual values, such as those of non-distillable 5o e and other impurities, metastases:

Having m the foregoing broadly described my wl i i cl i g i grfs s a d ir i ij g m rm t tig fi it invention, I shall now proceed to illustrate its tetrachloride an amount of copper between wm'kmg with the aid or actual examplesabout five grams and about ten grams, calculated Four portions of discolored commercial titanias ferrous sulfate, FeSO4 per liter of tetrachloum tetrachloride containing 0.15 percent vanadiride. boiling the mixture 'under refluxing comm calculatedon the T102 basis were Placed in tions and then distilling the so-treated titanium four separate glass distillation apparatus and retetrach1r1de ifluxed at about 136 9. in contact w th ground so 5. Method for purifying titanium tetrachloride DD ln'fl ow in Table and which comprises admixing with crude tetrachlothen distilled at normal pressure out of contact ride an amount of ferrous sulfate heptahydrato with materials other than glass and away from between about flve grams and about ten grams, contact with the outside atmosphere. calculated as ferrous sulfate, R804, per liter of The distillates were tested for vanadium which 68 tetrachloride, boiling the mixture under refluxisthe most objectionable discoloring impurity and ing conditions between about one hour and about their-color was noted. six hours, then distilling the so-treated titanium The'following Table I contains the results obtetrachloride.

. tained: WALTER F. MEISTER.

intended that such description examplc'sahall cluded gases which have not otherwise been re-" be interpret-ed as immsmg' um I.

the temperature of boiling. i. -e., about 136 c., a 35 Purifying'titamum Mmmmd' 

